The energy market today is growing so rapidly that, for example, gas turbine power generating plants sometimes already fail to satisfy the planned requirement on the day they are delivered. A quick subsequent increase in the output of the power generating plant can be obtained in principle by means of retrofitting the gas turbine. It is quite possible in this way to achieve increases in output of up to 20%. However, the increases in output must be adapted to the component of the lowest design rating, i.e. the component allowing the lowest increase in output, with the result that this component restricts the increase in output that is possible in a gas turbine power generating plant by retrofitting. This component is generally the generator, the copper temperatures of which form the limit for the increase in output obtained by retrofitting.
It is possible to lower the copper temperature of the generator by cooling. This may be achieved, for example, by cooling the generator inlet air, but also possible is a cooling circuit for the generator, in which a cooling device of the generator is supplied with cooled water, which absorbs heat there that is later extracted again from the heated water before it is returned to the cooling device. Such a cooling circuit is described, for example, in US 2008/0178590 A1. In it, the cooling of the heated water takes place either by an absorption chiller, which is driven by heated compressor air, exhaust gas of the gas turbine or steam of a steam turbine, or by a mechanical cooler, that is to say a cooler that is based on a mechanical compression process and is driven by electricity generated by the generator.
In particular if the heat for driving the absorption chiller is extracted from the compressor air or the steam of a steam turbine, this heat extraction must be taken into account when planning the management of the turbine. An extraction of electrical energy from the generator for driving a mechanical compressor reduces the possible useful output of the generator.